There has been proposed a fluidized-bed gasification facility for gasification of raw material such as coal, biomass or sludge wherein the raw material is supplied to a fluidized-bed gasification furnace preliminarily supplied with hot bed material or fluid medium, a gasification agent being supplied for formation of a fluidized bed to gasify the raw material, resultant produced gas being taken out outside while char produced upon the gasification in the gasification furnace and the bed material are supplied to a fluidized-bed combustion furnace to heat the bed material through fluidized combustion of the char, the heated bed material being supplied again to the fluidized-bed gasification furnace (see Patent Literature 1).
FIG. 1 shows a fluidized-bed gasification facility of the above Patent Literature 1. In FIG. 1, reference numeral 1 denotes a fluidized-bed combustion furnace into which char produced due to gasification of the raw material and the bed material in a fluidized-bed gasification furnace 2 is introduced through a lower portion of the combustion furnace, air from an air pipe 4 being blown through a bottom wind box 3. The char and bed material are fluidized and raised by the blown air; the char is burned and the bed material is heated while they are raised. Reference numeral 5 denotes a supplementary fuel port for supply of supplementary fuel to a fluidized bed in the fluidized-bed combustion furnace 1; and 6, a heat exchanger for heat recovery at a top of the combustion furnace 1.
Connected to the top of the combustion furnace 1 through a transfer pipe 7 is a separator 8 in the form of a cyclone and comprising outer and inner cylinders 9 and 10. Hot fluid including the bed material led out from the combustion furnace 1 to the transfer pipe 7 is tangentially introduced into the outer cylinder 9 where the fluid is centrifuged into the bed material and the exhaust gas. The exhaust gas with fine-grained ash is discharged through the inner cylinder 10 while the bed material 11 with rough-grained unburned char is supplied to the gasification furnace 2 via a downcomer 12 extending downward from a bottom of the outer cylinder in the separator 8.
The fluidized-bed gasification furnace 2 comprises an introduction section 13 into which the bed material 11 separated in the separator 8 is introduced through the downcomer 12, a gasification section 15 for gasification of raw material 26 supplied from a raw material feeder 14 by heat of the bed material 11, a communicating section 17 for supply of the bed material 11 in the introduction section 13 through a fluidized bed 16 to the gasification section 15 and a box section 18 extending over bottoms of the sections 13, 17 and 15 for supply of the gasification agent such as steam into the gasification furnace 2 and connected with a gasification agent supply line 19. The separation of the introduction and gasification sections 13 and 15 in the fluidized bed 16 by the communicating section 17 as shown in FIG. 1 prevents the burnt gas in the fluidized-bed combustion furnace 1 from flowing back through the fluidized-bed gasification furnace 2 to the separator 8.
The char not gasified in the gasification section 15 and the bed material are supplied for circulation to the fluidized-bed combustion furnace 1 via a circulation passage 25 comprising, for example, an overflow pipe, the bed material being heated again by the combustion of the char.
When coal is supplied as raw material 26 to be gasified to the gasification section 15, produced is produced gas 20 mixed with gas components such as hydrogen (H2), carbon monoxide (CO) and methane (CH4); when biomass or the like with a high water content is supplied as raw material 26 to be gasified, produced is produced gas 20 with the above-mentioned gas components containing much steam. The produced gas 20 is taken out via a take-out pipe 21 from the fluidized-bed gasification furnace 2 into a recovery device 22 where the produced gas 20 is separated from fine powder 23 entrained in the gas and is taken out through an inner pipe 24. The produced gas 20 thus taken out may be pressurized and supplied as fuel to, for example, a gas turbine, or may be supplied to a refinery for production of any target gas from the produced gas 20.
In order to guide the hot fluid from the fluidized bed combustion furnace 1 via the transfer pipe 7 to the separator 8, particles such as bed material entrained in the hot fluid must be prevented from being separated and accumulated in the transfer pipe 7 to clog the same; it is therefore envisaged that the separator 8 is arranged adjacent to the combustion furnace 1 to make the transfer pipe 7 as short in length as possible. In the construction of FIGS. 2 and 3, arranged above lateral corners of the fluidized-bed gasification furnace 2 adjacent to the fluidized-bed combustion furnace 1 are separators 8 and 8′ connected respectively via short transfer pipes 7 and 7′ to the combustion furnace 1 (see Patent Literature 2).
However, in the structure shown in FIGS. 2 and 3, the bed material 11 supplied via the downcomers 12 to the corners of the fluidized-bed gasification furnace 2 adjacent to the fluidized-bed combustion furnace 1 is allowed to flow in shortest courses 27 to the circulation passage 25, so that unreacted char flows out through the circulation passage 25 and a low-temperatured dead space 28 is produced in the gasification furnace 2 at a position away from the combustion furnace 1 where no bed material moves. This makes temperature in the fluidized-bed gasification furnace 2 uneven, disadvantageously resulting in lowering in gasification efficiency of the raw material 26 in the gasification furnace 2. In the above-mentioned fluidized-bed gasification facility shown in FIG. 1, the bed material 11 supplied through the downcomer 12 to the fluidized-bed gasification furnace 2 is allowed to flow in a shortest course to the circulation passage 25, so that low-temperatured dead spaces where no bed material 11 moves are produced on laterally opposite sides of the shortest course in the gasification furnace 2. As a result, like the structure of FIG. 2, the temperature in the fluidized-bed gasification furnace 2 becomes uneven, disadvantageously resulting in lowering in gasification efficiency of the raw material 26 in the fluidized-bed gasification furnace 2.
In order to overcome this, it has been conceived to provide a heat-resistant partition or partitions for regulation of a travel direction of the bed material 11 so as to move the bed material 11 to the dead space or spaces. In a structure shown in FIGS. 4 and 5, two heat-resistant partitions 32 are arranged in a laterally spaced-apart relationship and oppositely with respect to the circulation passage 25 such that the partitions 32 have their base ends firmly attached to a wall 29 of the gasification furnace 2 closest to the fluidized-bed combustion furnace 1 and have tip ends extending toward a wall 30 of the gasification furnace 2 farthest away from the combustion furnace 1 with communicating sections 31 therebetween. Thus, laterally symmetrical and substantially U-shaped circuitous flow passages 33 and 33′ are provided in the fluidized-bed gasification furnace 2 which are partitioned by the partitions 32 and in communication with each other at the communicating sections 31. A separator 8 is arranged above a right-side end in the circuitous flow passage 33 close to the wall 29, and a separator 8′ is arranged above a left-side end in the circuitous flow passage 33′ close to the wall 29. A take-out port 34 is arranged above and centrally of the circuitous flow passages 33 and 33′.
When the bed material 11 is supplied through the downcomers 12 to the right- and left-side ends of the one and the other circuitous flow passages 33 and 33′, respectively, the bed material 11 move through the respective circuitous flow passages 33 and 33′ in a direction away from the fluidized-bed combustion furnace 1 and joins via the communicating sections 31 to each other at the central passage toward the circulation passage 25. As a result, the bed material 11 can be caused to pass every corner without lingering of the bed material 11 in the laterally opposite dead spaces to keep uniform the temperature in the fluidized-bed gasification furnace 2.